Ancenis is a former commune in the Loire-Atlantique department in western France. On 1 January 2019, it was merged into the new commune Ancenis-Saint-Géréon. It is a former sub-prefecture of the department, and was the seat of the former arrondissement of Ancenis.
It played a great historical role as a key location on the road to Nantes, the historical capital of Brittany. It was named "the key of Brittany" and the door of Brittany.